Camcorders have a lot going for them. Autofocus means that as you zoom the lens, the image will still be sharp, as you pan or follow a moving subject, focus will adjust to match.
With a DSLR, focus is usually manual, lenses are not parfocal, meaning you must adjust focus as you zoom, and following a moving subject and keeping it in focus manually is very difficult, even when the camera is on a tripod.
All those limitations with a DSLR have solutions, and for professionally made Cinema, each shot is setup, actors positions are marked on the floor, distances are accurately measured, nothing is left to chance. Then, a good photographer and the focus puller who is the person who focuses the lens can keep subjects in sharp focus. Generally, zoom lenses are not used, but when they are needed, very expensive zoom lenses that are par focal are used.
That's why the 70D seemed interesting, because it does autofocus video. People expected better from the next generation of DPAF in the 7D MK II, but it stepped back a bit. Apparently, DPAF has some limitations that are a bit difficult to handle for focusing on moving subjects, or else Canon is reserving the additional capabilities for high end Cinema cameras.